Fig 2.

Mouse glioma growing in the brain is not permissive to oncolytic SFV or VV. (A) Day 6 DBT tumor-bearing mice were injected intracranially with Renilla luciferase-expressing SFV, with firefly luciferase-expressing VV, or with both viruses given either in the same injection or 48 h apart; virus replication was tracked by the IVIS in vivo imaging system over 5 days (72 h after the last administration of virus). Results show transient (up to 2 days) enhancement of SFV signal in mice that were sequentially treated (48 h apart) but not in those that were coinjected. Conversely, VV replication is strongly inhibited by simultaneous coadministration of SFV but not when SFV is given 48 h after VV. (B) Immunohistochemical analysis of brains sampled 24 h postinfection shows absence of infection of DBT tumor tissue deep in the brain by either SFV or VV or their comixture but prominent infection of healthy brain by SFV. VV is able to infect only DBT tumor tissue growing outside the brain parenchyma. (C) In contrast to the results obtained in vivo, SFV is able to infect DBT brain tumor explants and VV is able to enhance SFV replication in them. Tumor pieces were infected with 10⁷ PFU of each virus immediately upon extraction from the brain and visualized 24 h postinfection.